Posted
by
kdawson
on Monday February 18, 2008 @08:14PM
from the gardyloo-in-the-pacific dept.

An anonymous reader writes "Amateur satellite watcher Ted Molczan notes that a "Notice to Airmen" (NOTAM) has been issued announcing restricted airspace for February 21, between 02:30 and 05:00 UTC, in a region near Hawaii. Stricken satellite USA 193, which the US has announced plans to shoot down, will pass over this area at about 03:30. Interestingly, this is during the totality of Wednesday's lunar eclipse, which may or may not make debris easier to observe."

While perhaps a bit unconventional, there's a lot to be said for our government's decisive action here that could prevent a small-scale disaster if the satellite were to hit the ground. It seems like the prudent thing to do.

I find it quaint, the notion that the real reason they have to shoot the satellite down is because it has a tank of hydrazine onboard. Meanwhile, the Russians have let *freaking nuclear reactors* reenter our atmosphere. It's pretty transparent that they're A) trying to upstage the Chinese, and B) prevent any tech from making it into the hands of hostile parties. Even more transparent than the whole thing with A.Q. Kahn:

1) Pakistan funds its bloody nuclear program via nuclear equipment sales.2) The international community eventually can no longer look the other way.3) Khan steps forward. "Whoops, it was me! My bad. Every sale we made to every single country, I arranged, negotiated, and shipped everything, all with government aircraft, all of my own. No Musharraf involvement, nosiree!"4) Bush and Musharraf: "Bad Khan! Well, that case is solved."5) "House arrest", of the kind that lets you travel across the country. No charges pressed. Everyone wins.

I find it quaint, the notion that the real reason they have to shoot the satellite down is because it has a tank of hydrazine onboard. Meanwhile, the Russians have let *freaking nuclear reactors* reenter our atmosphere.

No offense, but comparing safety concerns of the US with the Russians is sort of bizarre. They are the country that used to just drop old reactor cores in the oceans after all. I honestly don't think they cared that they tossed radioactive waste across Canada any more than they cared what would happen when they build enormous nuclear reactors without containment domes. And if you think these are minor issues of environment protection then look up their involvement in the Aral Sea disaster. Russia is the antithesis [worldfrontpage.com] of environmental protection.

At least they never dared launch anything as crazy as Starfish Prime [wikipedia.org].

We are not the immaculate custodians of space that you seem to be picturing. Why, do you think, did we not shoot down the Delta II second stage that reentered in 1997 with a large amount of residual hydrazine and nitrogen tetroxide onboard? We have stages with signficant amounts of toxic residual fuel reenter all the time. Why, in the same year, when we had a Delta II explode *full* on liftoff, did the Air Force tell people in the *immediate area* that the smoke posed no danger? This was a *full launch vehicle*, not just a satellite's orbital maneuvering system. Do you have any idea how much beryllium we've had reenter? We sit by as large amounts of toxic materials enter all the time. As for the hydrazine itself, what do you think happens *on its own* to pressurized tanks of highly flammable fluids on reentry? I can't think of a *single* sizable object that's survived reentry still pressuretight.

First off, the US has NEVER claimed to be the "...immaculate custodians of space..." like you claim.Second off, regarding the Delta II second stage, it was believed based upon its size, speed, trajectory and form that it would burn up on reentry so the belief was we were OK. We know for sure that the satellite will survive reentry so we are trying to be proactive.Do we allow toxic material to reenter, Yes. Do we believe based upon size, speed, trajectory and such that the material will burn up, Yes. Can we

The Russians didn't drop old reactor cores into the ocean. They merely took a wrong turn on the way to ecologically responsible long-term storage facilities. Darn that Mapquest and its outdated Siberian directions. It was an honest mistake, Comrade.

The reactors sent into orbit are supposedly built to withstand re-entry and a crash landing. Firing explosives at a reator in LEO and potentially spreading fairy dust everywhere is probably worse than letting it form a crater in the ground where contamination can be contained.

Regardless of the 'real reason', shooting down the hydrazine is a GoodThing(TM).

The reactors distinctly do not reenter as a single chunk and leave a crater [wikipedia.org]. Cosmos 954, for example, scattered its fuel over a 370 mile path in the Canadian wilderness, leading to a search that covered 48,000 square miles, and later an even larger one. They only recovered 1% of the fuel.

It's pretty transparent that they're A) trying to upstage the Chinese, and B) prevent any tech from making it into the hands of hostile parties.

the only thing that's transparent is your bias. If they didn't try to shoot it down you'd claim it was "transparent" they didn't want to show the Chinese that they're capable of shooting it down, so they put lives at risk instead. In my opinion, you're one of those people who will criticize the US regardless of what it does.

"B) prevent any tech from making it into the hands of hostile parties" yes, because it's a big secret that spy satellites contain (whispers) cameras. shhh, don't tell anyone. It'd be a disaster if Al Queda found out. They might mount the camera on a donkey and fire it into orbit with a catapult.

Come on people. Occam's razor. We know that hydrazine is actually deadly. We know that Columbia's hydrazine tanks survived reentry. Colubia's tanks were empty, but this satellite's tanks will be full. The simplest explanation is that attempting to shoot it down doesn't increase the risk, but may substantially reduce the risk to humans. There's no down side. So that's why they're doing it. Take off your tin foil hat.

Wow, you're really unimaginative if all you can picture being on a satellite is cameras. Just as one possible example (among many, many possibilities): The US has spent the last decade trying to launch "stealth satellites". It has become the ultimate game for satellite spotters to try and find them. Not only do they regularly adjust their orbits, but they are believed to use articulated mirrors to try and reflect almost all light that hits them away from the Earth or onto remote locations, thus making th

That's pretty much a fair summary. When it comes to hard numbers and real facts (I.E. the stuff I know from my USN experience or from research matches their data closely), they are kinda trustworthy - but when it comes to analysis they are out to lunch. Way, way out to lunch.

FAS always raises hell over weapons tests of any kind. What else is new.

The SM-2 to be used is actually being MODIFIED with new software to try to do the intercept. It's not certain it'll work. So I guess that makes it a test.

The eclipse likely makes it easier to spot the "target".

But at least we aren't leaving a shitload of crap to fuck up usuable orbit space like the ChiComms did in their ASAT test. This bird is coming down NOW so why not test on it. It's cheap, if it works maybe we have a new use for an existing system w/o spending millions, we clean up our own mess by shooting it down, the debris will come down (with some risk as it's smaller pieces) and not clutter the crap out of orbital space, and we trash anything secret the enemy might try to capture (assuming it survived re-entry..but why risk it?). Sounds like a bargin "test" to me.

As others have pointed out in previous slashdot commentaries, there's even the risk that the explosion might send pieces of debris upwards in the atmosphere, and it may even reach an altitude that will not allow it to fall back down for a very long time

Do some basic research and don't believe everything you read on Slashdot. The missile they are firing (an SM-3) does not have an explosive warhead at all.

Now, instead of one big vaguely predictable chunk of technology falling down, we're going to have hundreds if not thousands of smaller chunks that are going to be absolutely impossible to predict their trajectory.

As someone whose day job is re-entry of large objects from near-orbital velocities I feel pretty qualified to respond to this. "vaguely predictable" is pretty generous. For the upper stage of a launch vehicle re-entering under an hour after launch (read: we know precisely where it is coming from, have the trajectory modeled, etc), there are thousands of miles in the "footprint" of the debris. And while most of it will come down in one or several big chunks, there will be a lot of scatter debris over that footprint. Now, think of something that's been in orbit for a number of years. Sure, we can observe it for a few months and try and nail the orbital parameters, but any way you slice it, it's an uncontrolled re-entry. We don't know with high precision the injection orientation, velocity, orientation, etc. That baby could have an uncertainty of 10,000 miles or more on it's footprint.

Also another note: big, dense, heavy things tend to break up very little on re-entry. They soak a lot of heat and come down hard and heavy. Big, light things like expended stages tear apart into little pieces and essentially dissipate in the atmosphere, leaving very little debris. And what debris remains, slows down very quickly, reducing scatter versus heavy pieces that just keep on flying. So there is a distinct advantage to breaking this thing into pieces. It will tear itself to shreds, versus coming down like a rock.

there's even the risk that the explosion might send pieces of debris upwards in the atmosphere, and it may even reach an altitude that will not allow it to fall back down for a very long time.

Don't believe everything you read on slashdot. What goes up must come down. The only way it will stay in orbit is if you give it the appropriate energy tangential to the surface of the earth to sustain an orbit, or more. That's it. I could shoot a bullet up into the sky right now at M=10,000, and it's either escaping the gravitational grasp of the earth or coming back to hit it. The chances of random pieces entering a stable orbit for the long term is slim. The chance of a few random pieces extending their stay? Granted, maybe for a few months to a year.

Actually, I heard a pretty argument that no debris produced by this could stay up for more than a few orbits. Basically, no matter what impulse you give to something at a certain point in its orbit, the new orbit and the old orbit will have that point in common. And that point is low enough in the atmosphere that any orbit crossing it will decay quickly.

In other words, the best you would get is a highly elliptical orbit that still crosses through the point of the explosion, but it will be circularized by the atmosphere. If a piece of debris is shot "upwards", than it will actually be in an orbit that includes an even lower point. That is, if it's moving upwards from the point, then during its next orbit, it will necessarily be below the point.

Actually, the final target tracking is most likely done either optically or by infrared. But, as I mentioned below, the area is in broad daylight at that time, and the Moon is below the horizon, so you're still quite correct to doubt that the Moon would interfere in any way.

I wonder what they mean by "shoot down"? It's not like an airplane, that if damaged, can't stay flying and falls to earth. If you blow up a big satellite, you end up with a bunch of little satellites, and that doesn't make them de-orbit much faster does it? I was under the understanding that blowing up stuff in space is BAD and creates a major headache more of space debris. I suppose if you really wanted to de-orbit a dead satellite you'd want to shoot a missile at it that would attach, and fire retro rockets to slow it down so it would degrade its orbit enough to hit atmosphere were it would be pulled down on its own from there.

They're not shooting at it to make it de-orbit, it's already de-orbiting. They are shooting at it to make sure that the hydrazine fuel tank doesn't make it down to Earth intact (or worse, almost intact).

Yeah right... The fact that it's a two-year old, highly-classified spy satellite has nothing to do with it. The *real* reason that they're spending $60M is to make sure that some fuel doesn't contaminate an acre or so of land.

I assume that anyone who can put a satellite into a stable orbit can also kill a foreign satellite. That may or may not be naive,

It is. Anyone who can fire a bullet cannot necessarily hit someone else's bullet out of the sky. (And there's no such thing as a "stable" orbit for most satellites, but that's neither here nor there.)

but it doesn't matter: Shooting at a foreign satellite is an act of war. When you do that and thereby start a war, the time of spy satellites is over anyway. The only options are not to shoot, for which you don't need the capability, or to shoot, and then the spy satellite is the least of your worries.

Spy satellites are at their most useful in a time of war. As are GPS satellites, which are used in a modern weapon system called a "JDAM", which is largely responsible for the high-precision warfare the US enjoys now.

In the event of a US-China War, expect China to shoot down GPS satellites before they even worry about air supremacy. And expect the US to launch them at a record pace.

Yeah right... The fact that it's a two-year old, highly-classified spy satellite has nothing to do with it. The *real* reason that they're spending $60M is to make sure that some fuel doesn't contaminate an acre or so of land.

Nothing useful in terms of spy gear is going to make it through re-entry. What might make it through re-entry is a large, resilient fuel tank containing high-toxic, probably carcinogenic, fuel. Logic dictates that if there was really something classified on the satellite that they didn't want to survive re-entry they simply would have designed it to not survive re-entry or they would have installed a self-destruct. Shooting it down at this point for the reason you're implying doesn't make sense.

Besides, if it's the gear (rather than the fuel) that concerns them then why haven't they bothered shooting down other de-orbiting sats in the past?

Along the lines of the self-destruct, I agree that a satellite which absolutely could not be allowed to return to Earth intact would be built with the proper destructive methods.

However, a self-destruct would also be useful in cases just like this, where the danger is not classified information, but hazardous materials. I am assuming that satellites are usually launched with the anticipation of decaying orbits, so why not build satellites with standard self-destruct for cases like this?
It seems like a

Because it's an accident waiting to happen. These satellites can cost anywhere from a few hundred million to a billion dollars, and to lose it because a software glitch causes the self-destruct system to go off would be bad. In addition, an explosive self-destruct system could litter orbit with debris.The best thing to do when a satellite needs to be removed from orbit is to de-orbit it with thrusters. Unfortunately, the computer on this satellite flaked completely soon after launch, and the de-orbit sys

...why not build satellites with standard self-destruct for cases like this?

First, a self destruct mechanism would add mass to the satellite, which takes mass away from other gear you'd like to add.

Secondly, if your satellite is not functioning, like this one, how would you activate the self-destruct mechanism?*

A possible third is security. What if "the enemy" were to get a hold of the self-destruct codes for all of our satellites? Shooting down a satellite with a missile is a much more costly and traceable event than sending out a radio signal and quietly killing them as th

Nothing useful in terms of spy gear is going to make it through re-entry. What might make it through re-entry is a large, resilient fuel tank containing high-toxic, probably carcinogenic, fuel. Logic dictates that if there was really something classified on the satellite that they didn't want to survive re-entry they simply would have designed it to not survive re-entry or they would have installed a self-destruct. Shooting it down at this point for the reason you're implying doesn't make sense.

Go look up Hydrazine (mono-methyl or di-methyl) and it's dangers. Tell ya what..heres the link to Wikipedia http://en.wikipedia.org/wiki/Monomethylhydrazine [wikipedia.org] and OSHA http://www.osha.gov/dts/chemicalsampling/data/CH_255500.html [osha.gov]
Think about how dangerous it is and how much of it is onboard (50kg or so). Then think about how much a good ambulance chaser aka "personal injury" lawyer could make off said dangers by suing Boeing, the Government and who knows else if someone's land was "contaminated" and there was an "injury". Then get back to me about if $60M is expensive.

I think this hydrazine thing is a red-herring. Think about it for a minute. So they say it's frozen, and in a really strong tank. But once that tank starts re-entering, the valves and hoses to it will be torn free. The heat of re-entry is going to unfreeze at least part of it. Now you've got venting ROCKET FUEL in the heat of a re-entry. I say at that point, the tank goes BOOM and there is nothing left... I think the real reason we are shooting this bird down is that it was launched in 2006 and has all our latest cool spy gadgets on it. We don't want them in an enemy's hands. So they cooked up this whole "hydrazine" problem to make it look like they are doing the world a favor. And they probably are. But I don't think its the hydrazine that is the problem here...

I had a chat with my grandfather who works on attitude control systems for commercial satellites about hydrazine. Hydrazine is used for attitude control and orbit stabilization. Since contact was never made with this USA 193, the hydrazine tank should be full. The ignition for hydrazine is heat, so all they do to fire it is have a little toaster that ignites a little bit of fuel at a time. Because the ignition source is heat, the hydrazine tank has to be incredibly well insulated to maintain a constant temperature. If the tank were to survive reentry, by being shielded by other components melting off, it would most likely rupture when it hit the ground at terminal velocity. Hydrazine is a pretty serious hazmat, and even a small concentration of that into your system will do serious, potentially permanent or even fatal damage to your lungs. Even worse, the hydrazine could ignite upon hitting the Earth and cause a small explosion, though the gas leak is more likely. If you took the surface of the earth and divided it into 1 acre chunks, I doubt more than 5% of those acres would have people in them( figure 10% of the Earth is inhabited, and large portions of that are farm) Nevertheless, a 1/20 chance of killing/permanently damaging anywhere from 1(hits near Bear Grylls in the desert) to 10,000 people(hits Rio), it certainly seems like a politically influenced decision to get rid of a potential disaster.

I'd expect that shooting a satellite whose orbit is already decaying might hasten the process by a couple days (smaller pieces would generally have a lower ballistic coefficient and therefore decay faster), but not by a significant amount.

The real benefit (to the US) is that turning a big, expensive satellite with lots of classified equipment on board into a bunch of little satellites means that the expensive bits are rendered unusable and far less likely to get to the ground intact, where they can be analyzed. It also provides a good opportunity to test a new missile system, and shows the Chinese that the US can play at their game, too.

But the US missile can launch from essentially any one of several Aegis-equipped cruisers, rather than needing a relatively fixed ballistic missile (like the Chinese system). The US missile is a descendant of the SM-1 Standard SAM developed to protect ships against aircraft and cruise missiles. The SM-3 version (to be used in the test) was developed specifically to intercept ballistic missiles--the only modification for this test is a software upgrade. I think it's already in regular service.

Actually, the classified hardware/software will burn up on reentry. Their more concerned about the full tank of hydrazine that would survive a normal reentry and create a hazardous materials nightmare near a populated area.
Since they suspect it is going to come down near Hawaii, I'd love to see some sort of Taco Bell stunt where TB gives away free tacos if the satellite lands in a volcano during the eclipse.

Actually, the classified hardware/software will burn up on reentry. Their more concerned about the full tank of hydrazine that would survive a normal reentry and create a hazardous materials nightmare near a populated area.

That's certainly believable if you can take Deputy National Security Advisor James Jeffrey at his word:

Yesterday, Deputy National Security Advisor James Jeffrey said the satellite's tank full of hydrazine rocket propellant was the main reason the military was planning to blast the orbiter. There's a small but real risk that the hydrazine tank could rupture, releasing a "toxic gas" over a "populated area," causing a "risk to human life."

Apparently man-made objects containing hydrazine propellant frequently rain down from the sky without incident, according to rocket scientists and space security experts [wired.com] who "scoff" at this rationale. And Joint Chiefs of Staff Vice Chairman Gen. James Cartwright doesn't seem too impressed either. But surely our Deputy National Security Advisor knows something about hydrazine that we don't.

Now who is this man James Jeffrey, you may ask?

It took more than two months, but the White House has finally found a new deputy national security adviser. And in the end, the administration didn't have to look very far.President Bush will appoint Ambassador James Jeffrey, a high-level State Department official who coordinates its Iran policy, according to people familiar with the matter. Jeffrey's appointment will be made later today, these people said.In his new post, Jeffrey will be National Security Adviser Steve Hadley's No. 2 and run most of the day-to-day operations of the National Security Council. The administration's new war czar, Deputy National Security Adviser Army Lt. Gen. Doug Lute, will take part in regular deputy's meetings chaired by Jeffrey.Jeffrey, a blunt-spoken and often-profane diplomat, will replace J.D. Crouch, an architect of the administration's controversial Iraq surge who resigned in May. Jeffrey has spent more time in Iraq than any other senior administration official. Prior to assuming his State Department post, he was the deputy chief of mission at the U.S. Embassy in Baghdad from June 2004 to March 2005, and as U.S. charge d'affaires to Iraq from March to June 2005.A colleague of Jeffrey's said that the White House would likely prove to be a better fit than the State Department had been. The colleague noted that Jeffrey is a staunch neoconservative, which left him often sharply at odds with other high-level State Department officials. Most of the neocons who once populated the administration left their posts in recent years as the Iraq war went off the skids. At the White House, though, Jeffrey will be able to work closely with two of the other surviving neocons: Deputy National Security Adviser Elliot Abrams and David Wurmser, one of Vice President Dick Cheney's top foreign policy staffers.

Source: Wall Street Journal, [wsj.com] July 19, 2007, four months before the information in the Iran NIE would be exposed, having been known to the White House since 2006.

Apparently man-made objects containing hydrazine propellant frequently rain down from the sky without incident, according to rocket scientists and space security experts who "scoff" at this rationale.

Well... This is one of those cases where there 'scientists' and 'experts' only tell half the truth - the half that supports an anti-Administration agenda. The other half of the truth is... all the cases they cite have roughly zip point nada in common with USA-193. In those cases, the tanks are empty or near

Don't be confused by the expression "shoot down". The satellite is still very high above the Earth. The cloud of debris will continue for many orbits and alternate between daylight and nighttime every 45 minutes, like every other low-orbit satellite.

Yep, but by the time the debris orbits into the Earth's shadow, about 15 minutes after the impact if my guesstimate is right, it will be entirely dark in visible wavelengths, shining only by reflected light. At that point, the lunar eclipse hinders rather than helps things, by removing a light source. And the eclipse moves out of totality within another 15 minutes after that.

Short version: The timing relative to the lunar eclipse is pure coincidence.

Unless it's a critical part of the top secret plan to propitiate Nyarlathotep and force Great Cthulhu back into an uneasy aeons-long slumber among the cyclopean ruins of R'lyeh, the fabled city of the Old Ones, looming over the black abyssal plain that lies miles below the sparkling sunlit waters of the Pacific.

In which case, I don't want to know what's in the payload of that missile.

At that point, the lunar eclipse hinders rather than helps things, by removing a light source.

Nope. Here's how it works:

1) a light source above the observer's horizon hinders visibility (can you see satellites when the Sun is up?)2) a light source below the observer's horizon but above the satellite's horizon helps visibility.3) a light source below both horizons doesn't do anything.

The eclipse reduces (1) compared to the full moon that would sit there otherwise, so it helps visibility by reducing a light source.

This post may or may not be a way to tell you that may or may not is a totally ambigious statement. Some people may or may not notice this. I may or may not be modded Offtopic but I can also be modded +1 Funny or +1 Insightfull. However, this may or may not be the case.

An airplane needs an engine to fly, and when that engine is destroyed and crashes somewhere near where you shot it down. A satellite needs no engine to fly, and when you shoot at it, it becomes thousands of little satellites, all of which continue to "fly" at 25,000 miles per hour.

I hope the people shooting at (not "down") this satellite have seen "Fantasia." In _The Sorceror's Apprentice,_ Mickey Mouse decides that the best way to deal with an out-of-control magic broom is to chop it into thousands of pieces... all of which just keep right on going, making the problem worse instead of better.

Unlike that example case, the many pieces of the satellite will not grow back into a whole satellite again. Each peice will be less massive and therefor less destructive upon impact with what will likely be the ocean if the attempt is successful.

The thing's low enough that all of it -- intact or in pieces -- will deorbit soon (days to weeks). And actually, smaller debris deorbits faster; there's more surface area per volume (and hence per mass), so drag from the not-quite-vacuum of the upper atmosphere decelerates small pieces faster.

An airplane needs an engine to fly, and when that engine is destroyed and crashes somewhere near where you shot it down. A satellite needs no engine to fly, and when you shoot at it, it becomes thousands of little satellites, all of which continue to "fly" at 25,000 miles per hour.

They might be counting on transferring enough momentum to the object for it to deorbit half an orbit later. That would put it over Africa, Asia and (possibly) Europe in longitude. I am not sure about latitude. I know that USA193 has an inclination of 60 degrees but that just ensures that it will be over land when crossing the longitude of Africa.

"Fantasia." In _The Sorceror's Apprentice,_ Mickey Mouse decides that the best way to deal with an out-of-control magic broom is to chop it into thousands of pieces... all of which just keep right on going, making the problem worse instead of better.

I liked the Itchy and Scratchy version better. It makes a better analogy too - when we breathe in the little tiny pieces of satellite, they will dissolve us from the inside out!

its not like there are pesky differences between the two, like one was in high orbit, one is about to enter the atmosphere with toxic cargo and the potential to kill people if it lands in the wrong area.

pah. No-one who knows anything about sats has any serious belief that this re-entry is any more of a danger to the general public than any other re-entry. The claims that sat might contain classified information that the military want to destroy is about as credible - i.e., not.

I doubt the lunar eclipse has anything to do with it. The timing is almost certainly based on the need to get the SBX [wikipedia.org] to sea and in position (it's not exactly a speedboat), and the best orbital conditions for the shot. The location was almost certainly based on the SBX being in Hawaii and having nice long empty stretches of ocean downrange for the SM-3 missile. (Both for the booster and for the payload to fall if it misses.)

Thanks for bringing the SBX to my attention. I was aware we had cool toys, but not THIS cool:

The radar is described by Lt. Gen Trey Obering (director of MDA) as being able to track an object the size of a baseball over San Francisco in California from the Chesapeake Bay in Virginia, approximately 2900 miles. The radar will guide land-based missiles from Alaska and California, as well as in-theatre assets.

The platform has many small radomes for various communications tasks and a central, large dome that encloses and protects a phased-array, 1,814 tonnes (4,000,000 pound) X band radar antenna. The radar is described as being 384 square meters, with "well over" 30,000 transmit-receive modules, which are arranged in a widely-spaced configuration. This configuration allows it to support the very-long-range target discrimination and tracking that GMD's midcourse segment requires. The array requires over a megawatt of power.

The SBX has been in Hawaii being repaired [blogspot.com], as it's a huge turd in seagoing terms [blogspot.com].
Can't cope with 8ft seas, and has no launch capability (as in, if you fall overboard you better start swimming, they ain't gonna pick you up).

No doubt goats will be slaughtered, wiccans consulted, and pentagrams drawn all in the hope that our missile intercept technology will actually work in a non-staged event.

And if it works? What then? How many successful test intercepts do you need before you think that the thing might actually work? Seriously, the only reason some folks are arguing that they don't think missile defense can work is because they do not like the politics of it. Eventually, missile defense can and will work. It's just an eng

Surely we will see, due to a "technical mistake", that the missile will just coincidently hit a Chinese, Russian, or Middle Eastern satellite. Or perhaps they will use this to draw everyone to Hawaii and shoot off a 2nd missile at an enemy satellite while everyone is busy.What will they blame this on? Since they have already used "a ship dropped it's anchor on the wire" for the Middle East Internet blackout, so here's some good excuses for our classic government:

IF they get a hit, then the explosion may or may not get blasted into space where it could do damage. Very small particles in space make a very big impact at say, 23,000mph, or faster still. Although we have great resolution on observing space junk in tiny sizes, we're doing the essentially the same thing that the Chinese did when they shot down an orbiter.

Azimuth, zenith, and charge value will dictate what happens. Might be a clean kill. Might not. I wouldn't take the Army's word for much, however, they

Well spirals are orbits, but ones which are perturbed by air resistance. If you ignore air resistance (and relativistic effects), then yes, all orbits would be perfect ellipses (or hyperbolas). In this case, the orbits of any debris will pass through the point of the explosion again, discounting air resistance. In reality, they will pass even lower, due to air (and in many cases, ground) resistance. They only way they could attain a stable (that is, higher than significant air resistance) orbit is if ha

Spy satellites (or any imaging/mapping sats) are usually in very circular orbits. Otherwise your image resolution gets degraded for most of the orbit (because you're farther away) and you have to constantly keep track to figure out what the actual resolution IS. As you pointed out, atmospheric drag tends to circularize things as well.

Okay, forget for a minute that the orbit is decaying. Whether or not a decaying orbit is "in orbit" is kind of a philosophical question.

So imagine the satellite in a stable orbit. Then you blow it up. So some pieces go flying in all directions. If you work out the orbital mechanics, every one of those pieces will be in a different orbit, but all of those orbits will pass through the point of the explosion. Caveats: this isn't true of orbits that intersect the ground first, or bits that, as you noted, get flung out of orbit altogether - that is, they achieve escape velocity. Escape velocity is awfully fast though, so that's probably not an issue here, and if something does hit escape velocity then it's not going to be a problem for us because that chunk of satellite will be GONE.

That's the reason you can't fire things into orbit with a gun (railgun, whatever), by the way. Any "orbit" you can put it into will have a point intersecting your gun. In order to put something in orbit that way you'd have to fire it out of the gun, then have a rocket on board to fire later and put it into an orbit that doesn't intersect the ground.

You can't actually escape the gravitation of anything, much less a planet. Technically, Earth, the sun, your toothbrush, will all pull on you (very weakly) no matter how far away you get. What you're thinking of is escape velocity, the speed at which you will never fall back, but continue on (slower and slower) outward forever.

Things we send into space can go a few different ways. If it's above escape velocity (Voyager, say) then it will never come back. If it's in a nice high orbit, way above the atmosphere (like geosynchronous satellites) then it will stay up for a LONG time. It will probably eventually come down, because there are always a few stray particles and things, but not for a long, long time. Things on a suborbital trajectory will come back down without circling the planet. Like SpaceShip One. Or you can have a low orbit, like spy satellites and the space shuttle. The atmosphere at that altitude is really thin, but not non-existent, so without thrusters to boost the orbit those sats will come back down, often on a fairly short time scale. The space station is fairly high (and massive) but if I recall correctly, it's orbit will decay in something less than a year without periodic boosting.

The problem with the satellite is that they've lost control. It isn't responding to commands. So it has lots of fuel (hydrazine) but the controllers have no way to fire the thrusters.

As someone else pointed out, orbital mechanics is kind of a counterintuitive thing. You'd think you could shoot things into orbit with a big enough gun, or that blowing up a satellite could boost some bits of it into stable orbits, but it turns out not to work that way. Something else weird: when you thrust in the same direction as you're traveling you slow down. You gain altitude, but you slow down - the opposite of what we normally expect. These satellite bits are speeding up (and losing altitude) due to atmospheric friction.

You don't have to pay me, of course, especially since slashdot screws up the spacing making them useless for copy/paste. I pulled them from this page [calsky.com] by clicking on the little Orbital Elements (TLE) button.